Yeast Harvesting Gravity Limits

So I've harvested a few batches of yeast from lower gravity brews (<1.060) at this point. Now I'm wondering, if you pitch the proper amount of yeast in the first place at what gravity does it become not such a good idea to harvest the yeast from a batch? I would think that if the proper amount of yeast is pitched, you could harvest off beers of 1.070 but I'm no yeast expert. That being said, I wouldn't consider harvesting off a brew that started much higher than 1.070. I know brewers yeast is alcohol tolerant but has it limits.

Most of my brews are in the 1.060 - 1.075 range and would like to know whether harvesting from these is a good idea or not.

Apologies if this has been discussed already but my searches weren't coming up with much.

Generally lower gravity lower hops equals best viability. At those gravity ranges it isn't ideal, but you probably would get away with a repitch, where it will really impact things is asking them to go multiple generations in that environment.

Bensiff said:

where it will really impact things is asking them to go multiple generations in that environment.

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Not quite sure I would agree with this idea, if the yeast have survived(actually thirived) the fermentation process once, why can't they do it again?

In a higher gravity beer you will just a larger yeast population, they work just as normal.

You start to stress the yeast and they start mutating. Repeated use will eventually change the yeast properties.

Calder said:

You start to stress the yeast and they start mutating. Repeated use will eventually change the yeast properties.

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No doubt that stressed yeast and repeated use will change the yeast. That is the reason I understand you generally do not want to harvest yeast past 5 or so generations.

My real question are what the general safe gravity levels are for harvesting. Maybe harvesting from a 1.065 beer is only good to reuse once instead of 5 times?? Maybe it's not good to harvest at all...

Seriously, this whole mutation thing has gone way out of control. It is not an issue. Don't wash your yeast if you are that concerned about it, but there is no REAL evidence of yeast mutation having any effect on the finished product.

I've heard around 5%ABV is approaching the max.

I disagree with theredben. Yes, you can still make beer with yeast from stronger batches, but can you make the best beer possible? If Chris White and Jamil say that the yeast are not optimal, I believe them.

Probably the phrase I hate to hear more than anything on HBT is "it worked for me." Of course it worked for you! Yeast are incredibly resilient. They will almost definitely convert sugar to alcohol no matter how you treat them. It's the diminishing returns we have to be concerned about. If someone just wants to make beer that's just good enough, then you can definitely relax your standards on repitching yeast. But I know that most of us are chasing the holy grail of the perfect beer.

How much more excited are you about your beer when they turn out amazing versus really good? Yeast is just one of those factors to achieving that.

theredben said:

Seriously, this whole mutation thing has gone way out of control. It is not an issue. Don't wash your yeast if you are that concerned about it, but there is no REAL evidence of yeast mutation having any effect on the finished product.

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As you repitch yeast you increase the amount of respiratory deficient mutants and at the same time there is a diminishing ability to reduce diacetyl. This suggests a correlation between the mutants and diacetyl issues (which cannot completely rule out the potential for gram positive bacteria being an issue here) according to George Fix based on research on lager yeast. As well, there are flocculation issues contributed to mutants.

theredben said:

Not quite sure I would agree with this idea, if the yeast have survived(actually thirived) the fermentation process once, why can't they do it again?

In a higher gravity beer you will just a larger yeast population, they work just as normal.

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Wyeast says so...they do not thrive in the high osmotic pressure of high gravity brews nor do they thrive in the high alcohol. Just because they can doesnt mean its good for them.

Think of it like this, its winter of 1944 and the 101st Airborne is surrounding Bastogne in its defense, its food, medical, and ammo are running low and the Germans are pushing hard to take the city. The 101st gave everything and stopped the Germans dead. When all was said and done many were dead and the rest are injured and exhausted. Now you have a choice, do you want those boys in that condition marching into Berlin? Or do you want a rested and equipped soldiers moving into Berlin?

Bensiff said:

Generally lower gravity lower hops equals best viability. At those gravity ranges it isn't ideal, but you probably would get away with a repitch, where it will really impact things is asking them to go multiple generations in that environment.

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I've heard someone on here mention hops ruining yeast viability before and I'm curious. Is that really true (to me it doesn't make any sense)? Why? Any references? I understand the lower gravity deal.

If you have a higher OG, you pitch more yeast. Not sure how this makes the yeast stressed unless you are approaching the ABV % limit for that paticular strain. Even then I am not sure this would matter.

Name dropping the big boys (Jamil, Palmer, etc) doesn't matter, there is no evidence that mutations have any effect. Lots of the homebrew pioneers had lots of ideas that were shown to have no positive effect. Just think about secondaries, it didn't hurt but was not absolitely neccesary. I think the same thing is going on here. Just a lot of caution. Nothing wrong with that, but it is important to make the distinction between caution and evidence based practises.

Bensiff - Your comment about osmostic pressure only applies when brewing a large beer. If you have cooaxed your yeast through any size, and then wash them you are removing the osmotic pressure. That is the whole ppoint.

rjwhite41 said:

I've heard someone on here mention hops ruining yeast viability before and I'm curious. Is that really true (to me it doesn't make any sense)? Why? Any references? I understand the lower gravity deal.

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Somewhere in The Brewing Network it is discussed, something to do with hop resins coating the cell walls. I can't find any scientific research on it with a quick search though, I would be interested to read actual research studies on it too.

Thanks for the discussion guys, this is all good stuff. I t makes sense to me that going through multiple generations or harvesting yeast from a beer with an abv higher than the yeast strains tolerance is going to diminish the viability and quality of the yeast.

But just for fun, lets say we agreed it was fine to harvest yeast to 3-4 generations if that yeast was under optimal conditions. What theredben says about the yeast not being stressed unless you are approaching the ABV % limit for that yeast strain makes a lot of sense to me.

Is the answer to my original question here more along the lines of "it is fine to harvest yeast from beers under the ABV % limit of that particular yeast strain"? So if the ABV threshold of my yeast is around 7%, I would think harvesting for one generation from a 6% beer would be fine.

Maybe I just need to break down and buy Chris White and Jamil's book on Yeast...

theredben said:

If you have a higher OG, you pitch more yeast. Not sure how this makes the yeast stressed unless you are approaching the ABV % limit for that paticular strain. Even then I am not sure this would matter.

Name dropping the big boys (Jamil, Palmer, etc) doesn't matter, there is no evidence that mutations have any effect. Lots of the homebrew pioneers had lots of ideas that were shown to have no positive effect. Just think about secondaries, it didn't hurt but was not absolitely neccesary. I think the same thing is going on here. Just a lot of caution. Nothing wrong with that, but it is important to make the distinction between caution and evidence based practises.

Bensiff - Your comment about osmostic pressure only applies when brewing a large beer. If you have cooaxed your yeast through any size, and then wash them you are removing the osmotic pressure. That is the whole ppoint.

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The question was can you pitch yeast collected from high gravity beers? Yes you can, but you can teabag a blender too, it doesn't mean its a good idea though. If Wyeast says it is not recommended I'm going to say they know what they are talking about and being the scientist they are will likely change their mind if evidence demonstrates it is not a legitimate recommendation.

Putting Dr. Fix into the category with JZ and Palmer is comical. Maybe since he did his work someone reported that the mutant issue has no basis, until I see evidence to the contrary I will take Fix's word on it. Even then, as Fix noted, there is potential that the mutant issue is not the main driver of some of the problems and they can be from things like bacteria that get a foot hold with multiple pitches. Whether you point your finger at yeast mutation or other factors, it remains a universal that multiple pitches result in a slow degradation of quality of the end product. If one has a lab and can selectively pull yeast to propogate new starters no big deal, for the bulk of homebrewers and probably many micro brewers that option is not on the table.

I thought my analogy was a good one. Take the cold Bastogne winter of 1944 and think of it as a high osmotic environment. You can take the soldier out of the cold and get them warmed up, but after a month sitting in a cold foxhole their bodies are warn out, it will take a lot more to recoup their strength given to fighting the cold than it would for a soldier fighting in Italy's warm climate (low osmotic pressure). The whole point is that a 1.060 + brew beats the crap out of the yeast like a winter in Bastogne and that is why it is recommended not to use yeast from high grav beers. Then there is the high ABV which is like the panzers shooting their 88's at the 101'st...you get the point. I'd rather have yeast that spent their last batch laying around fornicating in a nice envrironment than a bunch of warn out grizzled soldiers.

Anyway, if you can prove Fix and Wyeast wrong I'm all ears, I appreciate a good debate.

Bensiff said:

If Wyeast says it is not recommended I'm going to say they know what they are talking about and being the scientist they are will likely change their mind if evidence demonstrates it is not a legitimate recommendation.

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I don't know much about this debate, although I'm interested in both sides as I wash my yeast, but I'd just like to point out that Wyeast does have a financial incentive in making you believe you need to continue to purchase new yeast.

Just sayin'.

damdaman said:

I don't know much about this debate, although I'm interested in both sides as I wash my yeast, but I'd just like to point out that Wyeast does have a financial incentive in making you believe you need to continue to purchase new yeast.

Just sayin'.

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With a name like damdaman that is exactly the way of thinking I would expect . Anyway, in the same article Wyeast also notes that it would be cost prohibitive to use new yeast for a high grav brew suggesting to repitch from a low grav.

I've seen a lot of armchair quarterbacking on this subject but as far as I know nobody has tried and reported any differences. I say do it, and let us know if it works or not!

OldManHouston said:

So if the ABV threshold of my yeast is around 7%, I would think harvesting for one generation from a 6% beer would be fine.

Maybe I just need to break down and buy Chris White and Jamil's book on Yeast...

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Once again, of it course it will "work"... you'll make beer. And tons of us do it.

If you buy the book, you'll see that White and Jamil are all about optimizing your yeast. If I learned anything from the book, it's that they feel anything less than optimal is not good enough.

For example, there's a page in the book (sorry, let a friend borrow it so I can't reference) that shows successive generations of repitching a yeast that has been under-oxygenated with every pitch. By the 5th generation, the attenuation was 4 gravity points higher than the 1st, and it took at least an extra day to reach terminal gravity.

Overall, most people would not feel this is a horrible problem to have - but was it the perfect beer you set out to make? You really just have to ask yourself: how much under-performance you are willing to tolerate?

Personally I'll take a little because I like the harvesting process, saving a few bucks, and the thought that there's something perpetuating between all my batches. But if I start to see some significant problems, I'll start with a new pitch.

Good discussion here.

Bensiff said:

Even then, as Fix noted, there is potential that the mutant issue is not the main driver of some of the problems and they can be from things like bacteria that get a foot hold with multiple pitches. Whether you point your finger at yeast mutation or other factors, it remains a universal that multiple pitches result in a slow degradation of quality of the end product. If one has a lab and can selectively pull yeast to propogate new starters no big deal, for the bulk of homebrewers and probably many micro brewers that option is not on the table.

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Here is the crux of the issue, I believe that washing from batch to batch introduces bacterial populations that only grow higher. Personally I will just go from smack pack->wash->wash, then buy a new smack pack. If you are doing this on a commercial scale then you can properly acid wash to allow you more generations, but as a homebrewer by only going 2 wash cycles I can get 21 batches out of one pack, which is ~0.20$ per batch. Heck, even at only washing once, I can get 5 batches which is only 1.40$ per batch.

I am not disputing the fact that yeast mutate. I am only disputing that those mutations actually make a difference in the real world, not in a laboratory test.

I think it would really get into whether or not a particular mutation is able to get a foot and start negatively impacting things. Probably not after a few generations; however, again, the more you strain the yeast the more likely it is for such things. As well, the more strain would mean it would likely be easier for other nasties to get a foot hold...which would be more reason to avoid pitching yeast obtained from high grav brews and let the high grav brews be the final pitch of before getting fresh yeast.

I don't know if this is still a debate, but in a high gravity beer, why not take a small sample of your started to preserve the yeast?